![]() |
LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
|
subroutine cgeqr2p | ( | integer | M, |
integer | N, | ||
complex, dimension( lda, * ) | A, | ||
integer | LDA, | ||
complex, dimension( * ) | TAU, | ||
complex, dimension( * ) | WORK, | ||
integer | INFO | ||
) |
CGEQR2P computes the QR factorization of a general rectangular matrix with non-negative diagonal elements using an unblocked algorithm.
Download CGEQR2P + dependencies [TGZ] [ZIP] [TXT]
CGEQR2P computes a QR factorization of a complex m by n matrix A: A = Q * R. The diagonal entries of R are real and nonnegative.
[in] | M | M is INTEGER The number of rows of the matrix A. M >= 0. |
[in] | N | N is INTEGER The number of columns of the matrix A. N >= 0. |
[in,out] | A | A is COMPLEX array, dimension (LDA,N) On entry, the m by n matrix A. On exit, the elements on and above the diagonal of the array contain the min(m,n) by n upper trapezoidal matrix R (R is upper triangular if m >= n). The diagonal entries of R are real and nonnegative; the elements below the diagonal, with the array TAU, represent the unitary matrix Q as a product of elementary reflectors (see Further Details). |
[in] | LDA | LDA is INTEGER The leading dimension of the array A. LDA >= max(1,M). |
[out] | TAU | TAU is COMPLEX array, dimension (min(M,N)) The scalar factors of the elementary reflectors (see Further Details). |
[out] | WORK | WORK is COMPLEX array, dimension (N) |
[out] | INFO | INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value |
The matrix Q is represented as a product of elementary reflectors Q = H(1) H(2) . . . H(k), where k = min(m,n). Each H(i) has the form H(i) = I - tau * v * v**H where tau is a complex scalar, and v is a complex vector with v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i), and tau in TAU(i). See Lapack Working Note 203 for details
Definition at line 126 of file cgeqr2p.f.